Process of recovering sulfur from gas.



vented hydrogen from NITED sTArEs PATENT orrionl KARI: BURIQHEISER. OF HAMBURG, GERMANY.

PROCESS OF RECOVER-ING SULFUR FRQM GAS.

No Drawing.

1-5 a moist state, but also when baked, z. 6.

after the expulsion of the water. Ithas however been ascertained that a mass freed from Water by heating, only possesses ade- .quate reactivity when maintained atred heat during the passage of the gases. Tl'llS high temperature isobjectionable as it de stroys the valuable by-products contained in the gases. In general therefore, the 'ractice has been-touse'the purifying mass in a moist state, whichallows the process to be carried out at ordinary temperature. If the mass does not originally container genie matter, saw-dust may be added there tofor loosening and -moisture-reta1ning purposes.

- The absorbing capacity of such moist masses is however so slight, that large amount of space is required, and that the gas should flow but very slow, thus necessitating an apparatus of considerable dimensions.

The present invention is based on the fact that there is an int rmediate stage of-maximuni' absorbing capacity between the state of normalv hydrated iron oxid, capable of 40 acting as a purifier in a cold but moist -con-. dition, andthe' state of iron oxid obtained by expulsionof water from the hydrate, ca}

pable of acting in a dry state only when heated; at said intermediate stage the mass being. entirely free from moisture,

action at ordinary temperatures. This intermediate stage isrepresented .by that modification of hydrated iron orid, which is produced by gradualcexpulsionof the moisture' and of partof the chemically boundwater, Iuntil themass is neither hydrate nor oxidbut a partially hydrated ferric oxid.' The hydrated'iron oxid. undergoes several changes sharply distinguished from each'other by the coloring of the mass. The p rnoist bog-iron ore heretofore used for the Specification of Letters Patent.

Application filed July 26, 1910. Serial No. 573,928.

with. re-

Patented Feb. 27, 1912.

sulfur-purification is brown; when dried at 95 or 100 G. the color is changed to ocher. After partial expulsion of the chemically bound water a dark red coloring occurs, differing from the lightred or yellow-red of the oxid from which water has; been wholly expelled. The dark red coloring occurs when the mass is exposed for" some time to temperatures varying approximately between 100 and 200 C; a higher temperature is not injurious if the period of exposure is correspondingly, shortened. -It,is this red hydrate vwhich possesses an extremely high capacity of absorbing sulfureted hydrogen, the capacity being treble that-of the moist hydrate, and the timeof absorption being considerably increased.

The prepared partially hydrated ferric Y oxid, obtained by carefully regulated heating of bog iron ore or a similar, artificially prepared mass, is preferably used in a gran- I ular state; if it is in the form of powder, ag-

glomeration to a coarser granular state .may be effected by-adding a binding agent such as cement. By virtue .of its nature and qualities, the prepared mass requires no looseningadmixture, and in view of its dryness, there is no danger of caking' and baking the mass to solid lumps. The

large active surface afforded by the fine distribution and porosity is not counteracted by water, to be rendered partly ineffective. The rate of flow of-the .gas through the mass, hitherto usually 7 mm., may be increased to 200 mun, so that the dimensions of the purifying plant are greatly reduced.

Inasmuch as the gases flowing-through .the purifying mass jalways contain water vapor,'and as additional water is produced by the reaction binding the sulfureted hydrogen according to the following formula:

re o +au s r s +amo there is somedariger of depositing water on the mass, thereby chemically modifying the same, and diminishing the active surface.

.To allow the carrying out of the process attemperatures below 100 Centigrade, as is most desirable, the gases are maintained in a superheated state during their passage over the mass, that is to say, they are maintained in astate-in which they tend to absorb water. For this purpose, the gases maybe cooled before entering the purifier, and then reheated, or they are cooled as far as possible The-red hydrate of iron oxid is of course converted into iron oxid, by separation of v the restoration of heat below the tem erature at which the con-,

version is to ta e place in the purifier, and is made by heating the purifier. I

The regeneration of the mass which pref .erably takes place at temperatures between a bright red heat and about 200 C. may be effected in the simplest manner without 'removing it from the purifier, by passing air (oxygen) through the latter. It has been found that the considerable heat of reaction produced by the oxidation of the sulfur in the interior of the mass, more particularly with a rapid flow of the air, readily produces temperatures up to bright red heat.

the residual chemically bound water, so that the mass becomes unsuitable for the use'in' the manner described. This burning dead of the mass during regeneration can'be prevented by'providingfor a continuous, regular withdrawal of heat from the interidr of the-mass. ,This can be done by so dimensioning the purifying box, that its surface is comparativelylarge when compared with the contents, that is to say by using high,

narrow boxes; or cooling ribs or cooling pipes may bearranged to traverse the mass. In this manner the mass is prevented from becoming overheated, and the full absorbing capacity thereof'is restored.

The sulfurous acid produced by the oxi-' dation may be separately utilized, for example for bindingthe ammonia in the gas,

If the mass regenerated as described contains sulfate of iron, sulfite of iron, free acid and ammonium sulfite and sulfate (due to -the presence of ammonia in the gas), these melted sulfur accumulated at the bottom of the purifier, and was thus withdrawn from the oxidizing process. This separation of free sulfur may be explained as follows At the place where the air enters the purifying mass the oxidation of the sulfur is of course the most energetic by reason of the .temperature. 7 temperature advances in front of the oxidizexcess of oxygen. here present. The zone of oxidation is gradually extended through the purifier, in the direction of the flow of air, accompanied by a corresponding increase of A zone of somewhat lower ingliable'to clog the pipes. But if the air is flowing upward themelting zone is above the oxidizing zone; the melted sulfur trickles into the oxidizing zone, and is completely oxidized. This entirely obviates loss in cases in which the sulfurous acid from the purifier is utilized. I

A special method of preparing the red ferric hydrate from natural bog-non ore in the first instance consists in utilizing the peaty mass contained in the bog-iron ore for supplying the necessary heat, so that after once starting the process the conversion readily continues. For this purpose a furnace' is filled with lumps of bog-iron ore, whereupon a small fire is started at the bottom of the furnace. The peaty mass is thus ignited and the glowing zone gradually spreads through the entire charge, thereby expelling the moisture and also separating part of the chemically bound'water. If, as in ,the case of the regenerating process described, care is taken to maintain the temperature below bright red heat, the final product. is the-desired red ferric hydrate, which can be removed at the bottom, while a fresh charge is introduced at the top. The operation is thus rendered continuous.

' I'elaim':

1. Process of recovering sulfur from gas, which consists in heating a mass of by drated iron oxid to a temperature sufiicient only to produce the red hydrate modification thereof, and passing the gases containing sulfureted hydrogen over said modified mass at ordinary temperatures.

2. Process of recovering sulfur from gas, which consists in heating hydrated iron oxid to a temperature sufficient only to produce the red hydrate modification thereof, passing' the gases containing sulfureted hydrogen over said modified mass at ordinary temperatures, passing oxygen through said mass alternately with said gases, and with; drawing the heat of reaction produced durj ing the passage of the oxygen. 1 3. Process of recovering sulfur from gas which consists in heating hydrated'iro'n oxid to a temperature sufficient only to produce the red hydrate modification thereof, passing the gases containing sulfureted hydro-- gen over saidmodified mass at ordinary .temperatures, passing oxygen throu h the mass alternately with said gases, with rawing the heat of reaction produced during the passage of the oxygen through said mass, lixiviating the mass and reheating the same.

- 4, Process of recoveringsulfur from gas, which consists in heating hydrated iron oxid to a temperature 'sufficient'only to produce through alternately with said.. gases and withdraw;

gases saidmodified mass at ordinary 'tempera 5 the red hydrate modification. thereof, pass ing the gases contaming'sulfureted hydrogen over 'said.'modified mass, ,passin oxygen saidmass in an upward ir'ection,

ingthe heat" of reaction produced during the-passageof the oxygen.

5. Process of recovering sulfur from gas which consists in heating bog-ironxor'e-by igniting the peaty matter therein with a limited air supply to produce the red hy' drate modification thereof, and passing the containing sulfureted hydrogen over 6. Process of reco ering sulfur from gas mass at ordinary temperatures,

which consists iniheatingla mass of hy-.

dratediron oxid to'a tern erature suflicient only to produce the red tion thereof, and-passing the gaseicontaming sulfureted hydrogen over said, modified said gases 'bein'g previously co'oled below the point of water saturation.-

Intestimony, that I claim the foregoing as my invention '1 have signed my name in presence of two subscribing witnesses. I

ydrate modifica- 

